1. Field of the Invention
This invention relates to the use of certain clonidine derivatives to control ocular bleeding, such as the bleeding which occurs during opthalmic surgery. More particularly, the present invention relates to the use of hemostatic compositions containing clonidine derivatives (e.g., p-aminoclonidine) to decrease blood flow in the eye and thereby decrease bleeding resulting from ophthalmic surgery or other forms of ocular trauma.
2. Discussion of Related Art
The use of lasers in ophthalmic surgery is a fairly recent development in this field. Ophthalmic surgical procedures using lasers have been found to have numerous advantages over the more conventional techniques previously utilized.
There are many types of lasers currently known and in use, as well as those currently under development. The argon laser has heretofore been the principal type of laser utilized in ophthalmic surgery. The argon laser offers advantages over more conventional ophthalmic surgical instruments, but does suffer from some drawbacks. The use of other types of lasers in ophthalmic surgery has been and will continue to be the subject of scientific investigations directed to overcoming these drawbacks. Two other types of lasers which have been used experimentally are the YAG and Ruby Q-switched lasers.
The YAG and Ruby Q-switched lasers have been found to offer advantages over the argon laser. For example, it has been found that these lasers, unlike the argon laser, do not generate any significant amount of thermal energy in the eye during the surgical procedure. This characteristic is significant, since the thermal energy or heat generated in the eye by the argon laser can lead to tissue damage. However, it has also been discovered that the lack of heat generation by the YAG and Ruby Q-switched lasers results in a greater degree of bleeding during ophthalmic surgery. For example, it has been found that approximately 45% of human glaucoma patients undergoing iridotomies experience iris bleeding when the YAG and Ruby Q-switched lasers are utilized. The occurrence of bleeding from any vessel into the eye constitutes a significant complication during ophthalmic surgical procedures. For example, bleeding from the anterior segment of the eye is a complication which may result in compromised vision following an otherwise successful surgical procedure. Accordingly, a need exists for an ophthalmic hemostatic agent which is capable of decreasing ocular bleeding during surgical procedures utilizing this new generation of lasers.
The above-discussed ophthalmic surgical procedures utilizing laser technology may generally be described as "noninvasive." Ocular bleeding also constitutes a significant complication in the more conventional, invasive surgical procedures. Vasoconstrictors such as phenylepherine have been commonly used in some types of invasive ophthalmic surgery to produce mydriasis prior to the surgical procedure, with any ocular vasoconstriction which may have occurred being an incidental benefit. Unfortunately, mydriasis is to be avoided in patients suffering from glaucoma, and consequently the use of compounds having mydriatic properties is contraindicated in these patients. Accordingly, a need also exists for a hemostatic agent which is suitable for use in invasive ophthalmic surgery and does not cause mydriasis.
Although the foregoing discussion relates to the need for a hemostatic agent in ophthalmic surgical procedures, it is readily apparent that such agents would also be useful in many other ophthalmic conditions involving bleeding.